Konchog1 wrote:What would the Arhats' need? Bodhicitta and a better understanding of emptiness?
Arhat = game over.
If I may cite the Xiăopĭn Prajñāpāramitā Sūtra, Kumārajīva's Chinese, my own English and footnotes:
If a person has already entered into the status of certitude to perfection, they will be unable to arise mental aspiration toward anuttarā samyak saṃbodhi. For what reason? Because they have already constructed an embankment against the torrent of cyclic birth and death.
With a couple of pertinent footnotes:
 This is “samyaktva-niyāmam”. The Upadeśa provides an excellent discussion relevant here: Upadeśa 《大智度論》卷18：「如佛說。若有比丘於諸有為法不能正憶念。欲得世間第一法無有是處。若不得世間第一法。欲入正位中無有是處。若不入正位。欲得須陀洹斯陀含阿那含阿羅漢無有是處。」(CBETA, T25, no. 1509, p. 192, c10-17); = “As the Buddha taught: ‘If a bhikṣu is unable to correctly direct the mind with regards to conditioned dharmas, yet wishes to attain foremost mudane dharmas, this is impossible; if one does not attain foremost mundane dharmas, yet wishes to penetratively [realize] the unconditioned in the fixed status [of dharmas], this is impossible; if one does not penetratively [realize] the fixed status [of dharmas], yet wishes to attain śrotāpanna, śakṛādāgāmi, anāgāmi, or arhatva, this is impossible. … [and the formula in reverse.]”
This is the Mahāvibhāṣa Śāstra citing sūtra 《阿毘達磨大毘婆沙論》卷2：「…若不能起世第一法。能入正性離生。無有是處。若不能入正性離生。能得預流一來不還阿羅漢果。無有是處。」(CBETA, T27, no. 1545, p. 5, b9-18). See SN 25:1-10, iii 225-228; = Bodhi (2000: 1004-1007); and SN 13 Abhisamayasaṃyutta, Bodhi (2000: 621ff n219 = 787ff): “Both dhammābhisamaya and dhammacakkhupaṭilābha signify the attainment of stream-entry.” Mahāvibhāṣa Śāstra 《阿毘達磨大毘婆沙論》卷109：CBETA, T27, no. 1545, p. 563, c26-p. 564, a2); etc. Similar to: “stableness of the Dhamma (dhamma-ṭṭhitatā), the fixed practice of Dhamma (dhamma-niyāmatā)” (Bhikkhu Bodhi 2001: “Conditions”, II 12.20 and “Cases of Knowledge”, II 12.34 in Samyutta Nikāya, Wisdom: Boston. p. 551, 573.) – the first two: -ṭṭhitatā (住位性) & niyāmatā (定性). It is a stage of realization, just not yet nirvāṇa.
Thus, Conze’s “[ie. arhats who have reached their last birth, etc.]” is incorrect. It is a point of non-return, only, not finality. Thus, the “fixed status” is preceding realization of the ārya-phalas. This statement is found to be “attainment of stream-entry” (śrotaāpatti) in all the other three earlier sūtras (Dàoxíng, Dàmíngdù(A) and Chāojīng). Xuánzàng’s Dàbōrĕ(4) and (5) even specify it as “śrāvaka and pratyekabuddha certitude”, implying that the bodhisattva’s have a certitude, albeit of a different nature. This is also a critical idea later in the text.
 Sanskrit “baddhasīmāno hi te saṃsārasrotasaḥ”. Translation adds “torrent” to connect the metaphor of an “embankment” against a “flooding river”.
This is the very reason why so many Mahayana texts go to so much pain to warn bodhisattvas about falling to the stages of the sravakas or pratyekabuddhas. If one could become an arhat (or pratyekabuddha) and still turn back to the Mahayana, or, must turn back to the Mahayana, all those warning would not make any sense. Why not first become an arhat? The fact being, arhat = game over. End of samsara. So, no chance to develop the special qualities of a Buddha.
I thus take those texts which say otherwise, ie. that arhats can continue on with the Mahayana, to be neyartha teachings, ie. teachings which do not express the real truth of the matter, but are expedients requiring further explanation. Note that most of these neyartha teachings are later, even though they usually claim to be "the real truth". Such claims are more an indication of their own acknowledgement that they differ radically from established points of view.